1. Field of the Invention
This invention relates to a lens system, and more particularly relates to a wafer scale miniature image capture lens system.
2. Description of the Related Art
Mobile phones or personal computers employing imaging devices have become popular due to employment of solid-state image capture elements such as CCD (a charged coupled device) type image sensors, CMOS (a complementary metal oxide semiconductor) type image sensors and the like, allowing for higher performance and miniaturization of imaging devices. Additionally, there is demand for further miniaturization of image capture lenses loaded on the imaging devices.
However, despite demands, limits for further miniaturization of image capture lenses are being reached. As for the conventional image capture lenses, because they are true three dimensional structures and sensors therein need to also be miniaturized, it is difficult to control accuracy of lateral shift and tilt for each lens surface and fabrication thereof. Namely, fabrication tolerance is decreased.
FIG. 1 shows an imaging device using a published wafer scale lens module system. Light passes through the wafer scale lens modules 102 and 104 to the sensing element 106. In this art, the wafer scale lens modules 102 and 104 and the sensing element 106 can be fabricated by VLSI process technologies. Therefore, the image device can have a smaller size suitable for portable electronic devices, such as cell phones or personal digital assistants (PDAs). The wafer scale lens allows for further miniaturization along with technological advances driven by semiconductor processes such as Moore's law, as accuracy control is better. Moreover, while conventional lenses are fabricated by a discrete process, which assembles the lenses one by one, in contrast, the wafer scale lens is fabricated by a batch process, which can stack thousands of lens on a lens plate into a lens module array. However, despite the smaller volume, it is difficult to design a wafer scale optical lens system with good performance and high enough tolerance. Therefore, a wafer scale lens system with good performance and high tolerance is required.
Wafer scale optics has a lot of design constraints due to glass substrate structure and replication process limitations, such as limitations with lens material, substrate thickness, lens sag height and size, optical center alignment accuracy etc. For wafer scale lenses to become as main stream and as popular as plastic and glass lenses, wafer scale lens modules must have comparable optical design performance in accordance with appropriate manufacturing tolerance for the above described design constraints.